The invention relates to an X-ray source which is provided with a liquid metal target which flows through a system of ducts and is conducted through a duct section whose flow cross-section is reduced relative to that of the system of ducts. The invention also relates to an X-ray apparatus provided with such an X-ray source.
An X-ray source of this kind is known from DE 198 21 939.3. At the area of the reduced flow cross-section therein there is arranged a window, for example, of diamond, which is transparent to electrons and wherethrough high energy electrons (≈150 keV) can be directed into the liquid metal target so as to excite X-ray bremsstrahlung therein.
The aim is to construct the electron window to be as thin as possible (≈1-3 μm) so as to minimize the absorption of electrons and X-rays in the window (and hence also the heating thereof) and to achieve a high power of the X-ray source. The reduction of the cross-section results in a turbulent flow of the liquid metal target at the area of the window, said turbulent flow ensuring cooling of the window and a very effective dissipation of heat, so that the power density and the continuous loadability of the X-ray source can be further increased.
However, because the window separates the liquid metal target from a vacuum chamber, it must also have a minimum thickness which is so large that the reliability of operation, notably adequate pressure strength, is ensured in all realistic operating conditions. Optimization of the window in respect of an as small as possible thickness while providing at the same time adequate strength is particularly difficult notably because the turbulent flow involves the risk of formation of cavitations which are capable of exerting substantial forces on the window and the surrounding parts, for example, when the flow speed is unintentionally increased or the reduction of the flow cross-section becomes excessive because of the presence of foreign matter or manufacturing tolerances.